In an organic electroluminescent device, such as an OLED, a significant difference often exists between the external quantum efficiency and the internal quantum efficiency of organic electroluminescence, which substantially limits the development of OLEDs. The existing technology in the field can improve the external quantum efficiency of OLEDs by adding a capping layer, through which the luminous efficiency is increased by more than 30%.
The capping layer adopted in the existing technology often includes an inorganic layer or an organic layer. The inorganic layer is able to prevent moisture and oxygen from intruding into the OLED devices (e.g. OLED display panels) to a certain extent. Pixel shrinkage tests show that, an OLED device with an inorganic capping layer is subjected to a reduced erosion effect of moisture and oxygen on the light-emitting areas as compared to an OLED device without the inorganic capping layer. However, the inorganic capping layer has to be deposited by chemical vapor deposition (CVD) with strict deposition requirements. In addition, the inorganic capping layer has a low light extraction efficiency.
When the conventional inorganic layer in the capping layer is replaced with an organic layer, because of the substantially large refractive index n of the organic layer, the light extraction efficiency of the capping layer may be improved. However, when an organic layer is adopted as the capping layer and prepared using an inkjet printing (IJP) technique, the lifetime of the OLED device may be degraded. Thus, an OLED display panel, whose capping layer can be prepared using the inkjet printing (IJP) technique and, meanwhile, the light extraction efficiency is substantially high while the lifetime is not degraded, is highly desired in the field.
Further, when fabricating the capping layer including the organic layer, the surface of the fabricated capping layer may be uneven, showing bumps and hollows. An OLED display panel having a smooth capping layer is desired in the field.
The disclosed OLED display panel, fabrication method thereof, and electronic apparatus including the OLED display panel are directed to solve one or more problems set forth above and other problems.